Hybrid plate system and method

ABSTRACT

A bone plate system is disclosed which includes a bone plate having at least one plate hole, at least one pin adapted to be disposed in the at least one plate hole, and a polymer component disposed between the at least one pin and the bone plate. The polymer component includes a polymer that may be melted through the application of ultrasonic energy. The at least one pin is constructed of a material that will not melt under such application of ultrasonic energy. The re-solidified polymer component creates a bond between the at least one pin and the bone plate to provide a more rigid and secure mating therebetween, and to at least substantially prevent backout of the at least one pin with respect to the bone plate. A method of implanting the bone plate system is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/008,374 filed Dec. 20, 2007, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a bone plate system, and moreparticularly, to an improved hybrid bone plate system including a screwat least partially covered with a polymer component that is insertedinto the bone plate to achieve a secure fit.

Locked plating techniques offer an alternative biomechanical approachfor fracture fixation. Locking screw-plate systems act as single-beamconstructs in the bone, and the plate does not require compression andfriction generation to achieve mechanical stability. In locked platingsystems, screws or pins with threads on the undersurface of the head arethreaded into the plate, creating a fixed-angle device that does notallow screw toggle. Current clinical problems with such systems include:loosening of screw-plate connections; breakage/deformation ofscrew-plate connections; time consuming screw insertion;breakage/deformation of screws or blades in surgeries; andexplantation/material removals. Undesirable loss of screw purchase insome conventional systems is related to the failure of fixation systemsin osteoporotic bone or other weakened bone. Therefore, there is a needfor an improved bone plate system.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, these and other objectionshave been met by the invention of a bone plate system comprising a boneplate including at least one plate hole formed in the bone plate, atleast one pin having a head and a shaft and adapted to be disposed inthe at least one plate hole, and a polymer component disposed betweenthe at least one pin and the bone plate, wherein the polymer componentis made at least in part of a polymer which may be melted through theapplication of ultrasonic energy. In a preferred embodiment, the atleast one pin comprises a material that will not be melted through theapplication of the ultrasonic energy. Preferably, the material comprisesa polymer, and more preferably it comprises a metal.

In accordance with one embodiment of the bone plate system of thepresent invention, the polymer component comprises a coating applied tothe head of the at least one pin. In another embodiment, the polymercomponent comprises a coating applied to the shaft of the at least onepin. In yet another embodiment, the polymer component comprises aninsert disposed about the head of the at least one pin. Preferably, theinsert has an exterior surface configured to be substantially similar inshape to the exterior surface of the head of the at least one pin.

In accordance with another embodiment of the bone plate system of thepresent invention, the polymer component is constructed to bond the atleast one pin to the bone plate. In one embodiment the at least oneplate hole includes at least one helical ridge. In another embodimentthe at least one plate hole includes a series of concentric ridgesadjacent to one another. Preferably, the head of the at least one pinincludes at least one ridge.

In accordance with another embodiment of the bone plate system of thepresent invention, the at least one plate hole in the head of the atleast one pin each includes tapered surfaces such that the at least oneplate hole substantially mates with the head of the at least one pin,and the polymer component is disposed between the tapered surfaces ofthe at least one plate hole and the head of the at least one pin.

In accordance with another embodiment of the bone plate system of thepresent invention, the shaft is threaded. In another embodiment, thehead of the at least one pin further includes a projection disposedopposite the shaft, the projection being configured to mate with animplantation tool.

In accordance with another embodiment of the bone plate system of thepresent invention, the bone plate and the pin comprise biocompatiblemetals. In another embodiment, the pin comprises a biocompatibleceramic. In yet another embodiment, the at least one plate hole includesa lateral groove. In another embodiment the head of the at least one pinincludes a lateral groove. In a preferred embodiment, the at least onepin comprises a self-tapping screw.

In accordance with the present invention, a method of implanting a boneplate system has been discovered comprising the steps of positioning abone plate adjacent to a fracture in a bone, the bone plate having atleast one plate hole formed therein, inserting a pin through the atleast one plate hole and into a hole in the bone, providing a polymercomponent between at least the pin and the bone plate, melting thepolymer component through the application of energy, and allowing thepolymer component to re-solidify such that a bond is formed between thebone plate and the pin. Preferably, the melting step includes theapplication of ultrasonic energy. In a preferred embodiment, theinserting step includes the use of a driving force applied to the pin.

In accordance with one embodiment of the method of the presentinvention, the method includes pre-drilling the hole in the bone using aguide. In a preferred embodiment, the method includes pre-drilling thehole in the bone using the base plate as the guide.

In accordance with another embodiment of the method of the presentinvention, the pin comprises a self-tapping screw.

The bone plate used in the bone plate system of the present invention isused to maintain bone fragments in a rigid orientation while the boneheals. The present hybrid plate system and methods achieve such aresult. The hybrid plate system consists of a bone plate, at least onepin, and a polymer component. The polymer component not only forms astrong bond between the at least one pin and the bone plate, but alsoprovides enhanced stability between the at least one pin and theadjacent bone.

In use, in one aspect of the present invention, a pin and a polymercomponent are inserted through at least one plate hole in the bone plateand into the bone. The pin is driven using a force and ultrasonic energywhich melts the polymer component between the pin and the bone plateand/or the pin and the bone. The polymer component forms a bond betweenthe pin and the bone plate and/or the pin and the bone in order toprovide a complete and rigid connection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a bone plate secured to a boneaccording to an embodiment of the present invention.

FIG. 2 is a front perspective view of a pin and a polymer componentaccording to another embodiment of the present invention.

FIG. 3 is a front perspective view of the pin and the polymer componentshown in FIG. 2 in an assembled state.

FIG. 4 is a front perspective view of the pin and the polymer componentshown in FIG. 2 with a bone plate.

FIG. 5 is a front perspective view of an assembly of the pin, thepolymer component, and the bone plate shown in FIG. 4.

FIG. 6 is a side view of a pin according to another embodiment of thepresent invention.

FIG. 7 is an end view of the pin shown in FIG. 6.

FIG. 8 is a side perspective view of the pin shown in FIG. 6.

FIG. 9 is another side perspective view of the pin shown in FIG. 6.

FIG. 10 is a side cross-sectional view of a bone plate according toanother embodiment of the present invention.

FIG. 11 is a top view of the bone plate shown in FIG. 10.

FIG. 12 is a top perspective view of the bone plate shown in FIG. 10.

FIG. 13 is a side cross-sectional view of the pin shown in FIG. 6assembled with the bone plate shown in FIG. 10.

FIG. 14 is a top perspective view of the assembly shown in FIG. 13.

FIG. 15 is another top perspective view of the assembly shown in FIG.13.

FIG. 16 is a side cross-sectional view of a pin during insertion into abone plate according to another embodiment of the present invention.

FIG. 17 is a side cross-sectional view of the pin inserted into the boneplate shown in FIG. 16.

DETAILED DESCRIPTION

FIG. 1 depicts a first exemplary embodiment of a hybrid plate systemsecuring two bone fragments 103 and 118 together via a plurality of pins101. In FIG. 1, pins 101 are depicted as being unthreaded, although pinsaccording to the present invention may also be threaded. The hybridplate system includes at least one pin 101 and a bone plate 102 thatcontains at least one plate hole 106. Bone plate 102 may be comprised ofany biocompatible rigid material, for example, biocompatible metal. Pin101 includes a head 108, a shaft 109, a neck 111, and a tip 113. Pin 101may be comprised of any biocompatible rigid material, and is preferablycomprised of a material that will not be melted through the applicationof ultrasonic energy. Such a material may be a polymer, metal, ceramic,etc. Of course, if pin 101 is comprised of a polymer, it is preferablethat such a polymer not be susceptible to melting when an ultrasonicenergy is applied. Thus, the polymer comprising pin 101 would be of adifferent composition than that of a polymer component 104, which ismore fully described below. In another embodiment, pin 101 may includethreads on shaft 109 so that pin 101 may be threaded into one or morebone fragments. Head 108 is sized to correspond with plate hole 102,though an exact mating is not necessary or required.

Disposed on pin 101 is polymer component 104, which may entirely orpartially cover the surface of pin 101. Polymer component 104 can takeon many forms, such as a coating, layer, insert, ring, etc. For example,pin 101 may be coated with polymer component 104 prior to implantation,or polymer component 104 may be provided as an insert or ring at thetime of implantation. No particular form of polymer component 104 isknown to provide any advantage. Rather, polymer component 104 iscomprised of a polymer that melts under the application of an ultrasonicenergy.

Prior to use of the hybrid plate system, bone fragments 103 and 118 areoriented in a manner so as to be rigidly set. One or more bone holes 107may be drilled prior to the insertion of pins 101 by using bone plate102 as a guide. Alternatively, bone holes 107 may be drilled using aseparate guide or template. In yet another embodiment, pin 101 may be aself-tapping screw. Bone holes 107 preferably extend through thecortical portion 125 of bone fragments 103 and 118 and into thecancellous portion 126 of the bone. It is preferable that the dimensionsof bone hole 107 closely approximate the dimensions of at least aportion of pin 101 so that a mating fit may be established therebetween,though an exact mating is not necessary or required.

After bone holes 107 are formed in bone fragments 103 and 118, boneplate 102 is positioned adjacent to bone fragments 103 and 118 so thatplate holes 106 are aligned with the bone holes 107. Pins 101 are theninserted through plate holes 106 and into bone holes 107 to secure boneplate 102 to bone fragments 103 and 118, thereby positioning bonefragments 103 and 118 relative to one another and prevent movementtherebetween. Pins 101 are inserted through the use of force F₁ andultrasonic energy US. Force F₁ is preferably aligned with the axis ofshaft 109 in order to driving pin 101 through plate hole 106 and intobone hole 107. In addition, ultrasonic energy US may be simultaneouslyapplied with force F₁ so as to melt polymer component 104, whichsubsequently re-solidifies to provide a rigid bond and a more secure andexact mating between pin 101 and bone plate 102 and/or pin 101 and bonehole 107. Polymer component 104 substantially fills the space betweenpin 101 and bone plate 102 and/or pin 101 and bone hole 107. At leastone pin 101 may be inserted into each of the bone fragments 103 and 118to provide a rigid and stable connection between bone plate 102 and bonefragments 103 and 118.

FIGS. 2 through 5 depict another embodiment of a hybrid plate systemhaving a pin 201 and a polymer component 212 for insertion into boneplate 202 and one or more bone fragments. Polymer component 212 is inthe form of a ring and has a polymer component hole 227. Pin 201 has ahead 208, a shaft 209, a neck 211, and a tip 213. Polymer component 212is configured in an annular arrangement, though any arrangement whichallows shaft 209 to pass through polymer component 212 may be used.Shaft 209 is inserted into polymer component hole 227 until polymercomponent 212 is disposed about head 208. Polymer component 212 may beattached to pin 201 ultrasonically prior to insertion and attachment ofpin 201 to bone plate 202. Head 208 is conical and tapered, having asmaller diameter adjacent to neck 211 and a larger diameter oppositeneck 211. Polymer component hole 227 may be tapered to match thetapering of head 208. The tapered configuration of head 208 allowspolymer component 212 to slide onto head 208.

Either before or after its assembly with pin 201, polymer component 212may be machined or otherwise modified into a configuration which moreapproximately resembles the tapering of head 208 and the configurationof a tapered plate hole 206. Such a configuration is shown in FIG. 4. Itis noted that bone plate 202 may be configured as shown in FIG. 4, or itmay be taken as a section of a larger plate having two or more plateholes 206. The inside of plate hole 206 may include plate hole ridges214, striations, or other machined features to assist in fixation of thepolymer component to plate hole 206. Plate hole ridges 214 may be aseries of circumferential and concentric ridges adjacent to one another.Plate hole ridges 214 may alternatively be designed in athreaded-fashion whereby plate hole ridges 214 form one continuouswinding, spiral, or helical plate hole ridge 214. The purpose of platehole ridges 214 is to provide crests and valleys on the mating surfaceof plate hole 206 with which polymer component 212 and head 208 canmate, thereby further preventing or at least substantially hinderingbackout of pin 201 with respect to bone plate 202. After shaft 209 isinserted through plate hole 206, polymer component 212 contacts platehole ridges 214. Application of ultrasonic energy US melts polymercomponent 212 so that polymer component 212 conforms to plate holeridges 214 in plate hole 206 thereby forming a secure fit between pin201 and bone plate 202, as shown in FIG. 5. Pin 201 may also include apolymer component on shaft 209 which would also be melted by ultrasonicenergy US at the bone interface to form a bond between pin 201 and thebone.

Another embodiment of the present invention is depicted in FIGS. 6through 15. As shown in FIGS. 6 through 9, a pin 601 has a head 608, ashaft 609, and a neck 611. Shaft 609 has a tip 613 and a tapered edge617. Head 608 has a lip 616 positioned at the end of head 608 oppositeneck 611. Extending from head 608 opposite shaft 609 is a projection 615which may be used during insertion of pin 601 into a bone plate, toposition pin 601 thereafter, or for any other manipulative purpose.Projection 615 may be configured to receive an implantation tool, suchas an ultrasonic energy applicator and/or driving tool. Of course,projection 615 may be removed from pin 601 after implantation. Tip 613is shown, about which is disposed tapered edge 617.

FIGS. 10 through 12 depict a bone plate 602, which alternatively may beunderstood to be a portion of a larger bone plate. Bone plate 602comprises a plate hole 606 and an outer edge 620. Of course, it iswithin the scope of the present invention to provide a bone platesimilar to that depicted in FIGS. 10 through 12 but including two ormore plate holes 606 as desired. The configuration of such a bone platemay be of any size and shape to appropriately fit the bone or bones towhich it is to be anchored. Plate hole 606 has a tapered wall 621, suchthat plate hole 606 is wider near an upper surface 622 of bone plate 602and narrower near a lower surface 623 of bone plate 602. Outer edge 620of bone plate 602 is substantially annular in shape, but can take on anyother suitable shape, such as square, rectangular, triangular, etc.

FIGS. 13 through 15 depict bone plate 602 mated with pin 601. Pin 601 ispositioned through plate hole 606 such that head 608 is positionedagainst tapered wall 621. Head 608 is of a generally tapered orientationso that tapered wall 621 and head 608 mate to form a substantially tightfit. Disposed between plate hole 606 and head 608 is polymer component604.

FIGS. 16 and 17 depict a pin 1601 and bone plate 1602 in accordance withanother embodiment of the present invention. Pin 1601 comprises head1608, a shaft 1609, and a neck 1611. Both head 1608 and shaft 1609 aredepicted as being partially disposed within a plate hole 1606. The outerdiameter of shaft 1609 is substantially the same as the portion of platehole 1606 near a lower surface 1623 of bone plate 1602. Plate hole 1606is of a tapered configuration, having a tapered wall 1621 connectingupper surface 1622 and lower surface 1623. Plate hole 1606 has a smallerdiameter nearer to lower surface 1623 and a larger diameter nearer to anupper surface 1622 of bone plate 1602. Tapered wall 1621 includes platehole ridges 1614, which may be in the form of concentric rings or acontinuous spiral thread. Head 1608 contains a plurality of pin headridges 1624 similar in nature to bone plate hole ridges 1614. Pin headridges 1624 may also be comprised of a plurality of concentric rings ora continuous spiral thread. About head 1608 and pin head ridges 1624 isdisposed a polymer component 1604, in this case a coating. When pin 1601is inserted through plate hole 1606 via a force F, an ultrasonic energyUS is applied which melts polymer component 1604 which then fills thespace between head 1608 and tapered wall 1621. As polymer component 1604hardens or re-solidifies after insertion, plate hole ridges 1614 and pinhead ridges 1624 effectively anchor polymer component 1604 to itshardened location, thereby substantially preventing movement of head1604 relative to bone plate 1602. Plate hole ridges 1614 and pin headridges 1624 aid in maintaining the position achieved by the hardenedpolymer component 1604. Head 1608 may be designed such that, when fullyinserted into bone plate 1602, it does not project above upper surface1622 of bone plate 1602. Alternatively, it may be desirable for aportion of head 1608 to extend beyond upper surface 1622.

FIG. 17 depicts head 1608 in a substantially fully inserted positionwithin plate hole 1606. Polymer component 1604 is disposed between platehole ridges 1614 and pin head ridges 1624 to secure head 1608 to taperedwall 1621 of plate hole 1606 through the re-solidified polymer component1604. Due to the decreasing space between head 1608 and plate hole 1606during insertion, a portion of polymer component 1604 may run onto uppersurface 1622 and may then be removed.

According to a further embodiment, in order to more securely anchor ahead of a pin to a plate hole of the present invention, it iscontemplated that either or both of the head of the pin and the platehole include lateral holes or grooves. In one embodiment, the bone plateincludes one or more lateral holes or grooves that extend radially intothe bone plate from the plate hole. In another embodiment, the pin headincludes one or more lateral holes or grooves that extend into the headof the pin along at least a portion of its surface. Such lateral holesor grooves allow the polymer component, when melted, to become disposedwithin the lateral holes or grooves in order to further secure the headof the pin to the plate hole after re-solidification of the polymercomponent.

It is noted that polymer component according to any of the embodimentsof the present invention may be able to yield slightly relative to themore rigid materials which comprise the pin and the bone plate. Thisallows for slight movement between the pin and the bone plate as theadjacent bone and/or tissue heals.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made, and are encouraged to be made, to theillustrative embodiments without departing from the spirit and scope ofthe present invention as defined by the appended claims.

1. A bone plate system comprising: a bone plate having at least oneplate hole formed therein; at least one pin having a head and a shaft,said at least one pin adapted to be disposed in said at least one platehole; and a polymer component disposed between said at least one pin andsaid bone plate; wherein said polymer component is made at least in partof a polymer that may be melted through the application of ultrasonicenergy.
 2. The bone plate system of claim 1 wherein said at least onepin comprises a material that will not be melted through the applicationof said ultrasonic energy.
 3. The bone plate system of claim 2 whereinsaid material comprises a polymer.
 4. The bone plate system of claim 2wherein said material comprises a metal.
 5. The bone plate system ofclaim 1 wherein said polymer component comprises a coating applied tosaid head.
 6. The bone plate system of claim 1 wherein said polymercomponent comprises a coating applied to said shaft.
 7. The bone platesystem of claim 1 wherein said polymer component comprises an insertdisposed about said head.
 8. The bone plate system of claim 7 whereinsaid insert has an exterior surface configured to be substantiallysimilar in shape to an exterior surface of said head.
 9. The bone platesystem of claim 1 wherein said polymer component is constructed to bondsaid at least one pin to said bone plate.
 10. The bone plate system ofclaim 1 wherein said at least one plate hole includes at least onehelical ridge.
 11. The bone plate system of claim 1 wherein said atleast one plate hole includes a series of concentric ridges adjacent toone another.
 12. The bone plate system of claim 1 wherein said headincludes at least one ridge.
 13. The bone plate system of claim 1wherein said at least one plate hole and said head each includes taperedsurfaces such that said at least one plate hole substantially mates withsaid head, and said polymer component is disposed between said taperedsurfaces of said at least one plate hole and said head.
 14. The boneplate system of claim 1 wherein said shaft is threaded.
 15. The boneplate system of claim 1 wherein said head further includes a projectiondisposed opposite said shaft, said projection being configured to matewith an implantation tool.
 16. The bone plate system of claim 1 whereinsaid bone plate and said at least one pin comprise biocompatible metals.17. The bone plate system of claim 1 wherein said at least one pincomprises a biocompatible ceramic.
 18. The bone plate system of claim 1wherein said at least one plate hole includes a lateral groove.
 19. Thebone plate system of claim 1 wherein said head includes a lateralgroove.
 20. The bone plate system of claim 1 wherein said at least onepin comprises a self-tapping screw.
 21. A method of implanting a boneplate system comprising the steps of: positioning a bone plate adjacentto a fracture in a bone, said bone plate having at least one plate holeformed therein; inserting a pin through said at least one plate hole andinto a hole in the bone; providing a polymer component between at leastsaid pin and said bone plate; melting said polymer component through theapplication of energy; and allowing said polymer component tore-solidify such that a bond is formed between said bone plate and saidpin.
 22. The method of claim 21 wherein said melting step includes theapplication of ultrasonic energy.
 23. The method of claim 22 whereinsaid inserting step includes the use of a driving force applied to saidpin.
 24. The method of claim 21 including pre-drilling said hole in thebone using a guide.
 25. The method of claim 24 including pre-drillingsaid hole in the bone using said bone plate as said guide.
 26. Themethod of claim 21 wherein said pin comprises a self-tapping screw.